Comparison of Frequency and Time-Domain Iron and Magnet Loss Modeling Including PWM Harmonics in a PMSG for a Wind Energy Application

This paper presents the calculation of the electromagnetic losses for a 2.1-MW permanent magnet synchronous generator for wind energy application. The focus is on recognizing the significance of including the analysis of higher harmonics in the electromagnetic loss calculation. The analyzed harmonics include the ones resulting from the use of a pulse width modulation (PWM) of the voltage of the generator. The magnet losses calculated for the PWM current are several times higher than the ones calculated for the sinusoidal current. In addition, frequency-domain and time-domain models for iron loss calculation are compared. The frequency-domain model that assumes a sinusoidal variation and considers only the fundamental component of the magnetic induction in the stator core material underestimates the iron losses in the machine. Especially, when the additional losses resulting from the higher harmonics, rotational fields, and minor loops are taken into account. Finally, it is shown how the composition and thickness of the electrical steel used in the stator core of the generator influences the total core losses.